Acoustic Sensor (LTC1487CS8)

2014-11-01 20:30

Declaration:We aim to transmit more information by carrying articles . We will delete it soon, if we are involved in the problems of article content ,copyright or other problems.

This article describes the Acoustic Sensor (LTC1487CS8). The principle is very simple, very practical. The circuit components can help you understand better grasp this principle. For example, in this circuit, you can go to find and buy these components: LTC1487CS8.

This acoustic sensor was originally developed for an industrial application (monitoring a siren), but will also find many domestic applications. Note that the sensor is designed with safety of operation as the top priority: this means that if it fails then in the worst-case scenario it will not itself generate a false indication that a sound is detected. Also, the sensor connections are protected against polarity reversal and short-circuits. The supply voltage of 24 V is suitable for industrial use, and the output of the sensor swings over the supply voltage range. The circuit consists of an electret microphone, an amplifier, attenuator, rectifier and a switching stage. MIC1 is supplied with a current of 1 mA by R9. T1 amplifies the signal, decoupled from the supply by C1, to about 1 Vpp. R7 sets the collector current of T1 to a maximum of 0.5 mA. The operating point is set by feedback resistor R8.

Figure 1 Acoustic Sensor Circuit Diagram

The sensitivity of the circuit can be adjusted using potentiometer P1 so that it does not respond to ambient noise levels. Diodes D1 and D2 recitfy the signal and C4 provides smoothing. As soon as the voltage across C4 rises above 0.5 V, T2 turns on and theLEDconnected to the collector of the transistor lights. T3 inverts this signal. If the microphone receives no sound, T3 turns on and the output will be at ground. If a signal is detected, T3 turns off and the output is pulled to 24 V by R4 and R5. In order to allow for an output current of 10 mA, T3’s collector resistor needs to be 2.4 kΩ. If 0.25 W resistors are to be used, then to be on the safe side this should be made up of two 4.7 kΩ resistors wired in parallel. Diode D4 protects the circuit from reverse polarity connection, and D3 protects the output from damage if it is inadvertently connected to the supply.

Reprinted Url Of This Article:http://www.eeweb.com/blog/extreme_circuits/acoustic-sensor